Thomson River Fishway

The Thomson River Fishway is an exciting project that will help improve the health of an entire river system and protect the future of a vulnerable species of fish. Works are due to begin on the fishway in February 2019. The walking track and access to the tunnel will be closed from February to mid 2019.

The Thomson River is one of the region’s most significant and ecologically important rivers, and the creation of a fishway to allow passage between the Gippsland Lakes to the Victorian alpine region is a state priority.

The new fishway will unlock vast reaches of the upper Thomson and Aberfeldy rivers to endangered native fish for the first time in a century.

Extensive consultation has been carried out to ensure the fishway balances the significant heritage and cultural values of the site with the environmental improvement objectives.

Work will begin on the fishway at the start of February. There will be no public access to Horseshoe Bend from February until mid 2019.

Need

Horseshoe Bend Tunnel is four kilometres from Walhalla on the Thomson River. It was built in 1911 and 1912 to drain water from the Thomson at Horseshoe Bend to allow for alluvial mining of the river bed. It gained heritage status in 2002. If you’re interested in the history of the tunnel, please download a copy of the Heritage Report part one and part two.

Migration of native fish, such as the vulnerable Australian Grayling, have been stopped by the tunnel since its construction. The lack of river flow around Horseshoe Bend and the turbulent water from the tunnel provides a physical barrier for fish to swim upstream. The new fishway will see flows return to the original river course, with natural eddies and pools constructed to provide respite for fish as they journey upstream as part of their breeding cycle.

The Australian Grayling is a small to medium-sized, slender, silvery fish with soft-rayed fins. It lives in south-eastern Australia, including Victoria, Tasmania and New South Wales. It is a nationally vulnerable species listed under the federal EPBC Act.

The Grayling has a very short life span of 2-3 years and migrates throughout its life cycle between fresh and marine waters. Adult Grayling live in freshwater river systems. They move up and down the river looking for food and during autumn migrate to near the estuary to spawn. Its eggs are swept downstream to the sea and the adults return upstream. The young fish remain in the sea for about six months before returning to freshwater.

In our region it can be found in the Thomson, Macalister, Avon, Latrobe, and Tarwin rivers.

Planning

Extensive consultation has been carried out to ensure the fishway balances the significant heritage and cultural values of the site with environmental improvement objectives.

A project consultative committee of community, government agencies, WGCMA representatives and other stakeholders commissioned several designs and investigations before settling on a solution that shares the flows between the original river course and the tunnel.

We are grateful to have received considerable input from the project consultative committee, including members of the Hannaford family and the Friends of Horseshoe Bend Tunnel. Their suggestions strongly influenced the final design and the extensive research we completed will help ensure the project is done with as little impact to the heritage values as possible.

The fishway will be 200 metres long and ranging in depth from a maximum of 2.7m deep upstream down to no excavation downstream. The average depth is 1.4m. The width also varies to a maximum of seven metres wide. In context, the valley floor at Horseshoe Bend varies from 20m to 50m wide. Throughout the consultation period we have explored every option to minimise the size of the fishway. The result of this work is a low flow and a visually low impact fishway that will present itself as a meandering waterway (click on the before and after photos to see how it will look).

There are four main elements to allowing fish passage around Horseshoe Bend.

Technical experts, fish experts and engineers have helped us create a design that delivers just enough water for fish passage while still maintaining flows through the tunnel. A 60% to 40% split is proposed

The design of a fishway entrance, at the tunnel outlet, to attract fish past the outlet

Passage over existing rock riffles and;

A constructed fishway through the old river channel near the tunnel inlet.

During the creation of the fishway, the structural integrity of the tunnel will be closely monitored. There will be some impacts to the surrounding area, such as noise and dust from rock blasting, native tree removal, alterations and wear and tear to the access track, and modifications to the river bed.

Interested community groups and stakeholders will be kept fully informed of construction impacts, and their input sought where required.

When works are complete, full rehabilitation of the site will be our priority. Rehabilitation is expected to take between three and five years.

Outcomes

The photos below show what we expect the fishway to look like after works and rehabilitation are complete.

They include ‘before and after’ pictures to illustrate what is changing as a result of the fishway. If you click on the images you can see them in a larger format.

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Our organisation was established by the state government in 1997 to manage land and water resources in the West Gippsland region. We take this role seriously and our aim as a leader in natural resource management is to inspire partnerships and action to achieve improved catchment health.